JP2763224B2 - Organic nonlinear optical material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic nonlinear optical material, and more particularly, to an organic nonlinear optical material used in a wide range of fields such as optical computers, optical communication and optical information recording.

[0002]

2. Description of the Related Art Nonlinear optical materials are applied to means for generating coherent light such as amplification, oscillation and wavelength conversion of scattered light, and control of light characteristics such as waveform, spectrum, beam space characteristics, polarization and modulation characteristics. It is possible. Further, as a relatively new application, there are optical information processing elements such as a light space using a non-linear optical material, a temporally distortion-free transmission medium, a memory, and a switch.

One of the applicable fields using a material having a nonlinear optical effect is wavelength conversion of laser light (second harmonic generation: SHG). According to this phenomenon, it is possible to easily extract coherent light having a frequency twice that of the fundamental wave laser light and having the same properties as the fundamental wave laser light, and is widely used for information recording, image processing, laser measurement, and the like. The application can be expected in the field.

As a conventional nonlinear optical material, LiNb is used.
O ₃ (LN), KTiOPO ₄ (KTP), KH ₂ PO
Inorganic crystals such as ₄ (KDP) and NH ₄ H ₂ PO ₄ (ADP) have been used, but single crystals with high optical purity are very expensive, and some show deliquescent, which is inconvenient to handle. However, there are problems such as poor optical damage intensity and a low second-order nonlinear susceptibility. On the other hand, recently, expectations are growing for organic optical materials having faster response, higher optical damage strength, and an order of magnitude larger nonlinear optical performance index than inorganic substances, for example,
JP-A-1-281438, JP-A-2-13242
No. 3, JP-A-2-171730 and the like disclose a compound having no absorption in the visible region and exhibiting a high nonlinear optical effect. Also, JP-A-3-14628,
Japanese Unexamined Patent Publication No. 3-81746 discloses a nonlinear optical material in which a stable and large single crystal can be easily grown.

[0005]

The optical non-linearity (supramolecular polarizability β) at the molecular level of an organic material can be estimated from molecular orbital calculations, but the value of the supramolecular polarizability β at the molecular level can be estimated. Even if the organic material is large, if the crystal has a center of symmetry when crystallized, it becomes inactive at the crystal level. Therefore, whether or not the organic material exhibits high SHG activity cannot be determined only by the value of the supramolecular polarizability β, and it is a problem to actually synthesize and crystallize the organic material for evaluation.

Also, organic crystals of urea and aniline compounds have been announced as nonlinear optical materials, but none of these organic compounds have sufficiently satisfactory nonlinear and linear optical characteristics. MNA (2-methyl-4-nitroaniline) having an optical constant is also colored because its light absorption edge is on the long wavelength side (visible light region). Since the transmittance of light (particularly, blue light) is low, there is a disadvantage that the wavelength range is extremely limited.

Further, in putting an organic material into practical use as a nonlinear optical material, in addition to the above-mentioned problem of the transmitted light region, it is desired that the material be stable at room temperature and form a single crystal as large as possible. However, organic non-linear optical materials generally have poor thermal stability due to their low melting points, low dimensional accuracy, and difficulties in processing crystals, such as cutting and polishing, and in obtaining large single crystals. there were.

Further, when the melting point is low, the change in the refractive index at room temperature is large, so that there is a problem that the temperature tolerance of the phase matching condition is small. The present invention has been made in view of the above-mentioned problems, and is stable at room temperature and has SHG.
It is an object of the present invention to provide an organic nonlinear optical material having activity, capable of forming a crystal having no center of symmetry, excellent in transparency, and having an absorption edge wavelength in a short wavelength region.

[0009]

According to the present invention, structural formula (I)

According to the present invention, formula (I)

Embedded image The present invention provides an organic nonlinear optical material comprising a single crystal nitrobenzene derivative represented by the following formula:

The present inventors have proposed a supramolecular polarization method in which various acceptors and donors are introduced into a benzene ring by using a PPP (Pariser-Pearl Popple) method, which is one of semi-empirical molecular orbital methods. The β ratio and the maximum absorption wavelength λ _max were calculated, and the SHG activity in a crystalline state was evaluated by the powder method. As a result, 1,2-dihydroxy-4-nitrobenzene showed a wavelength of SHG light when a semiconductor laser was used. It has been found that a single crystal having no large absorption in the region, having excellent thermal stability, and having high SHG activity is formed.

1,2-dihydroxy-4 according to the present invention
-Nitrobenzene can be easily synthesized by a known method. For example, it can be synthesized by nitrating catechol (1,2-dihydroxybenzene) with nitric acid in ether. This reaction is preferably performed within a temperature range of 15 to 20 ° C for 2 to 3 hours.

The compound of the present invention can be prepared by a method known in the art,
For example, it can be used as a nonlinear optical material by purifying it by a recrystallization method, a sublimation method, or the like.

[0014]

EXAMPLES The present invention will be described in more detail with reference to Examples. First, 1,2-dihydroxybenzene was dissolved in diethyl ether, and nitric acid was added dropwise to this solution with stirring. After stirring for 2 hours, the solution was cooled to obtain crystals.
This was filtered, washed with diethyl ether, and then recrystallized with ethanol to obtain a single crystal of 1,2-dihydroxy-4-nitrobenzene. Further, by the same method, 2-nitroresorcinol,

[0015]

Embedded image 1,2-dimethoxy-4-nitrobenzene,

[0016]

Embedded image 1,4-dimethoxy-2-nitrobenzene,

[0017]

Embedded image 1-methoxy-2-hydroxy-4-nitrobenzene (JP-A-2-171730),

[0018]

Embedded image Was synthesized.

The spectrum, melting point and SHG intensity of the visible ultraviolet region of the 1,2-dihydroxy-4-nitrobenzene and nitrobenzene derivatives obtained in this example were measured. Table 1 shows the results.

[0020]

[Table 1]

FIG. 1 shows the spectrum of 1,2-dihydroxy-4-nitrobenzene obtained in this example in the visible ultraviolet region. Maximum absorption wavelength is 335nm
(In 1,4-dioxane). As is clear from Table 1 and FIG. 1, it is shown that the transmissivity is sufficiently high in the wavelength range of 415 nm, which is the SHG light of the semiconductor laser 830 nm, and that the transmissivity is sufficient even when a short wavelength induction light source is used. Has been shown.

The melting point of 1,2-dihydroxy-4-nitrobenzene was 175 ° C. as measured by DSC.
This has significantly improved thermal stability as compared with other 1-hydroxy-4-nitrobenzene derivatives. From this, it can be considered that the thermal stability was improved by the intermolecular hydrogen bonding. Next, SHG of the obtained 1,2-dihydroxy-4-nitrobenzene was evaluated by a powder method. A sample granulated to a diameter of about 100 μm is sandwiched between slide glasses, and this sample is placed on a Nd-YAG laser (wavelength =
(1.064 μm), green light having a half wavelength (532 nm) of the incident light was observed, and the second harmonic generated from the sample was detected by photomultiplier. Similarly, granulated urea was used as a standard sample, and the second harmonic intensity of urea was set to 1
And a relative comparison was made. As a result, 10 times the S of urea
It was found to show HG activity.

Further, 1,2-dihydroxy-4-nitrobenzene has good crystallinity and is stable at room temperature.

[0024]

The 1,2-dihydroxy-4 according to the present invention
-Nitrobenzene is an organic nonlinear optical material that is stable at room temperature, has good crystallinity, has relatively high SHG activity, has excellent transparency, and has a short absorption wavelength in a relatively short wavelength region. Therefore, it can be used for various nonlinear optical devices including a wavelength conversion element, and is an important material for practical use.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the wavelength and the absorbance of 1,2-dihydroxy-4-nitrobenzene according to the present invention.

Continuation of front page (56) References JP-A-6-507439 (JP, A) JP-A-2-171730 (JP, A) JOURNAL OF MATERIAL ALS CHEMISTRY, VOL. 1 NO. 5 PP. 775-780 (September 1991) C.I. LAMBERTH ET. AL. , “PREPARATION AND SECOND-HARMON IC GENERATION PROP ERIES OF TRIS (PYR OCATECHOLATO) STAN ATE (4) COMPAUNDING SERVICE GROUP. 1147 PP. 61-72 (1989) T. CHENG ET. AL. , "NONRESONANT EFISH AND THGSTUDIES OF NONLINEAR OPTICAL PROPERTY AND MOLE CULAR STRUCTURE RE LATIONS OF BENZEN E, STILBENE, AND OTH ER ARENE DERIVATIV ES " (58) investigated the field (Int.Cl. ^6, DB name) G02F 1/35 504 CA (STN)

Claims (1)

(57) [Claims] 1. A compound of the formula (I) An organic nonlinear optical material comprising a single crystal nitrobenzene derivative represented by